1. Field of the Invention
The present invention relates generally to methods and compositions that can be used to treat or inhibit cancers susceptible to protein kinase modulation. More specifically, the invention relates to methods and compositions which utilize compounds or derivatives commonly isolated either from hops or from members of the plant genus Acacia, or combinations thereof.
2. Description of the Related Art
Signal transduction provides an overarching regulatory mechanism important to maintaining normal homeostasis or, if perturbed, acting as a causative or contributing mechanism associated with numerous disease pathologies and conditions. At the cellular level, signal transduction refers to the movement of a signal or signaling moiety from outside of the cell to the cell interior. The signal, upon reaching its receptor target, may initiate ligand-receptor interactions requisite to many cellular events, some of which may further act as a subsequent signal. Such interactions serve to not only as a series cascade but moreover an intricate interacting network or web of signal events capable of providing fine-tuned control of homeostatic processes. This network however can become dysregulated, thereby resulting in an alteration in cellular activity and changes in the program of genes expressed within the responding cell. See, for example, FIG. 1 which displays a simplified version of the interacting kinase web regulating insulin sensitivity and resistance.
Signal transducing receptors are generally classified into three classes. The first class of receptors are receptors that penetrate the plasma membrane and have some intrinsic enzymatic activity. Representative receptors that have intrinsic enzymatic activities include those that are tyrosine kinases (e.g. PDGF, insulin, EGF and FGF receptors), tyrosine phosphatases (e.g. CD45 [cluster determinant-45] protein of T cells and macrophages), guanylate cyclases (e.g. natriuretic peptide receptors) and serine/threonine kinases (e.g. activin and TGF-β receptors). Receptors with intrinsic tyrosine kinase activity are capable of autophosphorylation as well as phosphorylation of other substrates.
Receptors of the second class are those that are coupled, inside the cell, to GTP-binding and hydrolyzing proteins (termed G-proteins). Receptors of this class which interact with G-proteins have a structure that is characterized by 7 transmembrane spanning domains. These receptors are termed serpentine receptors. Examples of this class are the adrenergic receptors, odorant receptors, and certain hormone receptors (e.g. glucagon, angiotensin, vasopressin and bradykinin).
The third class of receptors may be described as receptors that are found intracellularly and, upon ligand binding, migrate to the nucleus where the ligand-receptor complex directly affects gene transcription.
The proteins which encode for receptor tyrosine kinases (RTK) contain four major domains, those being: a) a transmembrane domain, b) an extracellular ligand binding domain, c) an intracellular regulatory domain, and d) an intracellular tyrosine kinase domain. The amino acid sequences of RTKs are highly conserved with those of cAMP-dependent protein kinase (within the ATP and substrate binding regions). RTK proteins are classified into families based upon structural features in their extracellular portions which include the cysteine rich domains, immunoglobulin-like domains, cadherin domains, leucine-rich domains, Kringle domains, acidic domains, fibronectin type III repeats, discoidin I-like domains, and EGF-like domains. Based upon the presence of these various extracellular domains the RTKs have been sub-divided into at least 14 different families.
Many receptors that have intrinsic tyrosine kinase activity upon phosphorylation interact with other proteins of the signaling cascade. These other proteins contain a domain of amino acid sequences that are homologous to a domain first identified in the c-Src proto-oncogene. These domains are termed SH2 domains.
The interactions of SH2 domain containing proteins with RTKs or receptor associated tyrosine kinases leads to tyrosine phosphorylation of the SH2 containing proteins. The resultant phosphorylation produces an alteration (either positively or negatively) in that activity. Several SH2 containing proteins that have intrinsic enzymatic activity include phospholipase C-γ (PLC-γ), the proto-oncogene c-Ras associated GTPase activating protein (rasGAP), phosphatidylinositol-3-kinase (PI-3K), protein tyrosine phosphatase-1C (PTP1C), as well as members of the Src family of protein tyrosine kinases (PTKs).
Non-receptor protein tyrosine kinases (PTK) by and large couple to cellular receptors that lack enzymatic activity themselves. An example of receptor-signaling through protein interaction involves the insulin receptor (IR). This receptor has intrinsic tyrosine kinase activity but does not directly interact, following autophosphorylation, with enzymatically active proteins containing SH2 domains (e.g. PI-3K or PLC-γ). Instead, the principal IR substrate is a protein termed IRS-1.
The receptors for the TGF-β superfamily represent the prototypical receptor serine/threonine kinase (RSTK). Multifunctional proteins of the TGF-β superfamily include the activins, inhibins and the bone morphogenetic proteins (BMPs). These proteins can induce and/or inhibit cellular proliferation or differentiation and regulate migration and adhesion of various cell types. One major effect of TGF-β is a regulation of progression through the cell cycle. Additionally, one nuclear protein involved in the responses of cells to TGF-β is c-Myc, which directly affects the expression of genes harboring Myc-binding elements. PKA, PKC, and MAP kinases represent three major classes of non-receptor serine/threonine kinases.
The relationship between kinase activity and disease states is currently being investigated in many laboratories. Such relationships may be either causative of the disease itself or intimately related to the expression and progression of disease associated symptomology. Rheumatoid arthritis, an autoimmune disease, provides one example where the relationship between kinases and the disease are currently being investigated.
Autoimmune diseases result from a dysfunction of the immune system in which the body produces autoantibodies which attack its own organs, tissues and cells—a process mediated via protein phosphorylation.
Over 80 clinically distinct autoimmune diseases have been identified and collectively afflict approximately 24 million people in the US. Autoimmune diseases can affect any tissue or organ of the body. Because of this variability, they can cause a wide range of symptoms and organ injuries, depending upon the site of autoimmune attack. Although treatments exist for many autoimmune diseases, there are no definitive cures for any of them. Treatments to reduce the severity often have adverse side effects.
Rheumatoid arthritis (RA) is the most prevalent and best studied of the autoimmune diseases and afflicts about 1% of the population worldwide, and for unknown reasons, like other autoimmune diseases, is increasing. RA is characterized by chronic synovial inflammation resulting in progressive bone and cartilage destruction of the joints. Cytokines, chemokines, and prostaglandins are key mediators of inflammation and can be found in abundance both in the joint and blood of patients with active disease. For example, PGE2 is abundantly present in the synovial fluid of RA patients. Increased PGE2 levels are mediated by the induction of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) at inflamed sites. [See, for example van der Kraan P M and van den Berg W B. Anabolic and destructive mediators in osteoarthritis. Curr Opin Clin Nutr Metab Care, 3:205-211, 2000; Choy EHS and Panayi G S. Cytokine pathways and joint inflammation in rheumatoid arthritis. N Eng J. Med. 344:907-916, 2001; and Wong B R, et al. Targeting Syk as a treatment for allergic and autoimmune disorders. Expert Opin Investig Drugs 13:743-762, 2004.]
The etiology and pathogenesis of RA in humans is still poorly understood, but is viewed to progress in three phases. The initiation phase where dendritic cells present self antigens to autoreactive T cells. The T cells activate autoreactive B cells via cytokines resulting in the production of autoantibodies, which in turn form immune complexes in joints. In the effector phase, the immune complexes bind Fcf receptors on macrophages and mast cells, resulting in release of cytokines and chemokines, inflammation and pain. In the final phase, cytokines and chemokines activate and recruit synovial fibroblasts, osteoclasts and polymorphonuclear neutrophils that release proteases, acids, and ROS such as O2-, resulting in irreversible cartilage and bone destruction.
In the collagen-induced RA animal model, the participation of T and B cells is required to initiate the disease. B cell activation signals through spleen tyrosine kinase (Syk) and phosphoinositide 3-kinase (PI3K) following antigen receptor triggering [Ward S G, Finan P. Isoform-specific phosphoinositide 3-kinase inhibitors as therapeutic agents. Curr Opin Pharmacol. Aug.; 3(4):426-34, (2003)]. After the engagement of antigen receptors on B cells, Syk is phosphorylated on three tyrosines. Syk is a 72-kDa protein-tyrosine kinase that plays a central role in coupling immune recognition receptors to multiple downstream signaling pathways. This function is a property of both its catalytic activity and its ability to participate in interactions with effector proteins containing SH2 domains. Phosphorylation of Tyr-317, -342, and -346 create docking sites for multiple SH2 domain containing proteins. [Hutchcroft, J. E., Harrison, M. L. & Geahlen, R. L. (1992). Association of the 72-kDa protein-tyrosine kinase Ptk72 with the B-cell antigen receptor. J. Biol. Chem. 267: 8613-8619, (1992) and Yamada, T., Taniguchi, T., Yang, C., Yasue, S., Saito, H. & Yamamura, H. Association with B-cell antigen cell antigen receptor with protein-tyrosine kinase-P72(Syk) and activation by engagement of membrane IgM. Eur. J. Biochem. 213: 455-459, (1993)].
Syk has been shown to be required for the activation of PI3K in response to a variety of signals including engagement of the B cell antigen receptor (BCR) and macrophage or neutrophil Fc receptors. [See Crowley, M. T., et al., J. Exp. Med. 186: 1027-1039, (1997); Raeder, E. M., et al., J. Immunol. 163, 6785-6793, (1999); and Jiang, K., et al., Blood 101, 236-244, (2003)]. In B cells, the BCR-stimulated activation of PI3K can be accomplished through the phosphorylation of adaptor proteins such as BCAP, CD19, or Gab1, which creates binding sites for the p85 regulatory subunit of PI3K. Signals transmitted by many IgG receptors require the activities of both Syk and PI3K and their recruitment to the site of the clustered receptor. In neutrophils and monocytes, a direct association of PI3K with phosphorylated immunoreceptor tyrosine based activation motif sequences on FcgRIIA was proposed as a mechanism for the recruitment of PI3K to the receptor. And recently a direct molecular interaction between Syk and PI3K has been reported [Moon K D, et al., Molecular Basis for a Direct Interaction between the Syk Protein-tyrosine Kinase and Phosphoinositide 3-Kinase. J. Biol. Chem. 280, No. 2, Issue of Jan. 14, pp. 1543-1551, (2005)].
Much research has shown that inhibitors of COX-2 activity result in decreased production of PGE2 and are effective in pain relief for patients with chronic arthritic conditions such as RA. However, concern has been raised over the adverse effects of agents that inhibit COX enzyme activity since both COX-1 and COX-2 are involved in important maintenance functions in tissues such as the gastrointestinal and cardiovascular systems. Therefore, designing a safe, long term treatment approach for pain relief in these patients is necessary. Since inducers of COX-2 and iNOS synthesis signal through the Syk, PI3K, p38, ERK1/2, and NF-κB dependent pathways, inhibitors of these pathways may be therapeutic in autoimmune conditions and in particular in the inflamed and degenerating joints of RA patients.
The hops derivative Rho isoalpha acid (RIAA) was found in a screen for inhibition of PGE2 in a RAW 264.7 mouse macrophages model of inflammation. In the present study, we investigated whether RIAA is a direct COX enzyme inhibitor and/or whether it inhibits the induction of COX-2 and iNOS. Our finding that RIAA does not directly inhibit COX enzyme activity, but instead inhibits NF-κB driven enzyme induction lead us to investigate whether RIAA is a kinase inhibitor. Our finding that RIAA inhibits both Syk and PI3K lead us to test its efficacy in a pilot study in patients suffering from various autoimmune diseases.
Other kinases currently being investigated for their association with disease symptomology include Aurora, FGFB, MSK, RSE, and SYK.
Aurora—Important regulators of cell division, the Aurora family of serine/threonine kinases includes Aurora A, B and C. Aurora A and B kinases have been identified to have direct but distinct roles in mitosis. Over-expression of these three isoforms have been linked to a diverse range of human tumor types, including leukemia, colorectal, breast, prostate, pancreatic, melanoma and cervical cancers.
Fibroblast growth factor receptor (FGFR) is a receptor tyrosine kinase. Mutations in this receptor can result in constitutive activation through receptor dimerization, kinase activation, and increased affinity for FGF. FGFR has been implicated in achondroplasia, angiogenesis, and congenital diseases.
MSK (mitogen- and stress-activated protein kinase) 1 and MSK2 are kinases activated downstream of either the ERK (extracellular-signal-regulated kinase) 1/2 or p38 MAPK (mitogen-activated protein kinase) pathways in vivo and are required for the phosphorylation of CREB (cAMP response element-binding protein) and histone H3.
Rse is mostly highly expressed in the brain. Rse, also known as Brt, BYK, Dtk, Etk3, Sky, Tif, or sea-related receptor tyrosine kinase, is a receptor tyrosine kinase whose primary role is to protect neurons from apoptosis. Rse, Axl, and Mer belong to a newly identified family of cell adhesion molecule-related receptor tyrosine kinases. GAS6 is a ligand for the tyrosine kinase receptors Rse, Axl, and Mer. GAS6 functions as a physiologic anti-inflammatory agent produced by resting EC and depleted when pro-inflammatory stimuli turn on the pro-adhesive machinery of EC.
Glycogen synthase kinase-3 (GSK-3), present in two isoforms, has been identified as an enzyme involved in the control of glycogen metabolism, and may act as a regulator of cell proliferation and cell death. Unlike many serine-threonine protein kinases, GSK-3 is constitutively active and becomes inhibited in response to insulin or growth factors. Its role in the insulin stimulation of muscle glycogen synthesis makes it an attractive target for therapeutic intervention in diabetes and metabolic syndrome.
GSK-3 dysregulation has been shown to be a focal point in the development of insulin resistance. Inhibition of GSK3 improves insulin resistance not only by an increase of glucose disposal rate but also by inhibition of gluconeogenic genes such as phosphoenolpyruvate carboxykinase and glucose-6-phosphatase in hepatocytes. Furthermore, selective GSK3 inhibitors potentiate insulin-dependent activation of glucose transport and utilization in muscle in vitro and in vivo. GSK3 also directly phosphorylates serine/threonine residues of insulin receptor substrate-1, which leads to impairment of insulin signaling. GSK3 plays an important role in the insulin signaling pathway and it phosphorylates and inhibits glycogen synthase in the absence of insulin [Parker, P. J., Caudwell, F. B., and Cohen, P. (1983) Eur. J. Biochem. 130:227-234]. Increasing evidence supports a negative role of GSK-3 in the regulation of skeletal muscle glucose transport activity. For example, acute treatment of insulin-resistant rodents with selective GSK-3 inhibitors improves whole-body insulin sensitivity and insulin action on muscle glucose transport. Chronic treatment of insulin-resistant, pre-diabetic obese Zucker rats with a specific GSK-3 inhibitor enhances oral glucose tolerance and whole-body insulin sensitivity, and is associated with an amelioration of dyslipidemia and an improvement in IRS-1-dependent insulin signaling in skeletal muscle. These results provide evidence that selective targeting of GSK-3 in muscle may be an effective intervention for the treatment of obesity-associated insulin resistance.
Syk is a non-receptor tyrosine kinase related to ZAP-70 involved in signaling from the B-cell receptor and the IgE receptor. Syk binds to ITAM motifs within these receptors, and initiates signaling through the Ras, PI 3-kinase, and PLCg signaling pathways. Syk plays a critical role in intracellular signaling and thus is an important target for inflammatory diseases and respiratory disorders.
Therefore, it would be useful to identify methods and compositions that would modulate the expression or activity of single or multiple selected kinases. The realization of the complexity of the relationship and interaction among and between the various protein kinases and kinase pathways reinforces the pressing need for developing pharmaceutical agents capable of acting as protein kinase modulators, regulators or inhibitors that have beneficial activity on multiple kinases or multiple kinase pathways. A single agent approach that specifically targets one kinase or one kinase pathway may be inadequate to treat very complex diseases, conditions and disorders, such as, for example, diabetes and metabolic syndrome. Modulating the activity of multiple kinases may additionally generate synergistic therapeutic effects not obtainable through single kinase modulation.
Such modulation and use may require continual use for chronic conditions or intermittent use, as needed for example in inflammation, either as a condition unto itself or as an integral component of many diseases and conditions. Additionally, compositions that act as modulators of kinase can affect a wide variety of disorders in a mammalian body. The instant invention describes compounds and extracts derived from hops or Acacia which may be used to regulate kinase activity, thereby providing a means to treat numerous disease related symptoms with a concomitant increase in the quality of life.